Lower-than-Expected economy after two months

Discussion in 'Prius v Fuel Economy' started by Weirderal, Dec 23, 2019.

  1. Weirderal

    Weirderal New Member

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    Hello everyone!

    I just got a 2012 Prius v with 115,000 miles on November 1st. Pretty pleased overall so far, but I'm a little confused seeing everyone saying they're getting fuel economy near or above the level of the EPA estimate on here.

    I've been doing all the computations myself at the pump (gallons inserted/trip A reading; reset every time), after seeing the computer was consistently overestimating it by a small margin (1-2 gallons).
    My best tank was around 39 mpg, a couple between 37-38, and on this last one I just got 33. 283 miles/8.5 gallons.

    I live in Harrisburg (which is somewhat hilly), drive a ~3 mile commute every weekday, and every other weekend or so I drive an hour and a half out to friends or family, cruise control on at ~70 on the highway.

    In town I'm forced to give it a good push uphill at lights and such to keep up with traffic, but I'd like to think I'm not being particularly aggressive overall. (If this says anything about my driving: I was getting 14.5-15 miles per gallon with my '97 Econoline that this replaced, which seemed to be above average for those.) I always seek the Eco light.

    I don't use the different modes except on very rare occasions when I'm stopped on a highway ramp and I'll engage the power mode, just until I'm up to speed. But that happens less than once a week.

    I'm not getting any warning lights or anything else that would scream at me that I'm doing something wrong.
    Tires are at about half-tread.
    Any silver bullets I'm missing?

    Thank you.
     
  2. Ronald Doles

    Ronald Doles Member

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    Mileage is going to vary slightly on identical make/models. Although quality control has improved dramatically over the years there are still tolerance variations engine to engine that affect mileage. Some vehicles might have all those tolerances stacked in the right direction and will see improved mileage others not so much.

    I see that you are in Pennsylvania. A lower temperature affects mileage as the engine takes longer to warm up. Many short trips where the car has to warm up each time yield worse mileage than one longer trip. The Prius has an auxillary electric heater that comes on to speed up the cabin heat but it is a drain on the traction battery. It is minimized in Eco mode. Has it gotten colder in the last few weeks?

    Tires affect mileage. Low rolling resistance tires help a bit. Tire inflation is more important on high milers because it affects rolling resistance and you are trying to wring out every mpg.

    Terrain that you are driving over affects mileage.

    The biggest unknown is the driver.

    The EV, Eco, Power mode selection for the most part affects the sensitivity of the throttle pedal, the amount of regenerative braking and the electric cabin heater. Eco is obviously best but the pedal is the least sensitive in that mode.

    It may take you a while to figure out what works to get the best mileage for you.
     
    #2 Ronald Doles, Dec 24, 2019
    Last edited: Dec 24, 2019
  3. dig4dirt

    dig4dirt MoonGlow

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    I would say the 3 things not in your favor.

    1) 3 mile commute.
    The Prius needs to go thru a "warm up" stage
    The engine will start and go thru some stages and use gas.
    The mpg will suffer, but slowly climb over miles of driving, however 3 miles and not so much.

    2) Colder climate.
    Being in PA myself, we are now in cold territory.
    The Prius needs to run the engine to supply heat for cabin climate control so if you use it
    for your 3 mile commute, the engine would prob run constant.


    I myself have a 3 mile commute and I DO NOT USE THE HEAT. If I did, my "c" would get
    about 30mpg compared to the 45-50mpg I get now in the winter.
    Our 2015 Gen3 Prius takes our kids to school 1.1 mile roundtrip, with 3 trips to school a day!
    MPG for that prius under 30mpg without HEAT lol.

    We finally can park in our garage, so hope to not have to defrost the windshield,
    because that can also DROP the mpg much much more, as it uses engine heat.

    Both our Prius do get longer drives like you, so the mpg goes a little higher on those trips

    In the spring/summer, the mpg WILL RAISE for you as the temps raise in PA
    as you will use the climate control less, and the engine will not have to run as long to get
    thru its warm up stages.

    You can read more the Prius warm up stages, I think it is 5 stages.

    And also...

    3) Cruise Control Speed
    You had said 70 mph on the highway.
    The Prius has a mph/mpg curve and the faster you go, the lower your economy will be.
    I am not sure on the "v" but should be very similar to the standard liftback.
    I am not saying 70mpg is too fast, I am saying that it will also decrease mpg, but it
    will actually boost the mpg overall in the winter of your daily 3 mile commute

    @bwilson4web has done vast research and charted this data up.
    Perhaps he can equate his knowledge on the small hit the "v" would be?

    I have been installing the "radiator" block, it is some foam plumbing tubing on the front grill
    to block wind and allows less cool down of the engine and such.
    You can read up on this, very easy DIY mod that can yield results esp in your case.
    I also just installed an engine block heater on both my Prius.
    HOWEVER it is not all that effective, but it does help some. (any little bit helps o_O )
    Although in another thread, I had mentioned that I would not wish Gen3 engine block heater install
    on my worse enemy:cry:.
    And cost wise may not be worth it for a dealer install.
    @Mendel Leisk can also shed light to install and his xp on engine block heater
    But I did install for ease of mind, and also to help with warm up stage and faster climate control when needed.
    May also be false thinking, but I think may also be less stress on the engine over time

    You could do a lot of reading about mpg, but overall should not worry too much about it,
    as in the warmer seasons, you will see an increase in mpg
     
    scona, bisco and Aaron Vitolins like this.
  4. mikefocke

    mikefocke Prius v Three 2012, Avalon 2011

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    Yes, you can experiment and see the speed versus MPG effect thanks to the v's dash display of instantanious MPG. Just drive at various speeds and see what happens.

    Check your tire pressure now it is winter.

    Use the proper weight oil

    Drive with a light foot. Allow more merging distance.

    Winter caused mine to drop noticeably but I still averaged over 40 MPG for the 50k some miles I owned it. I lost maybe 3 MPG. But I wasn't trying to drive 3 miles at 70 MPH. Think of the amount of air flowing through a cold radiator onto the engine block and keeping it from getting warm enough to go into normal hybrid mode. Plus your body is cold so running the heater and/or front window defrost which is sucking heat out of the engine through the anti-freeze that circulates through the heater core. Until the thermostat opens the v is essentially an ICE powered car.
     
  5. bisco

    bisco cookie crumbler

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    at 115,000 miles, i would read up on the egr circuit cleaning/oil catch can threads
     
    bwilson4web likes this.
  6. fuzzy1

    fuzzy1 Senior Member

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    Have you read this post? It covers the most common low-mpg issues:
    Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new

    However, it doesn't cover old-car issues. One such item is excessive brake pad drag, which you can detect by wheel hubs getting too warm or hot.

    MPG always falls in winter, due to lower-energy seasonal fuel blends, colder ambient temperatures, increased need for cabin heat, drag-producing water on the road, etc.:
    Why mileage gets worse in winter


    My first comments, overlapping some previous replies:

    3 mile commutes from a cold start are too short to reach good MPG in any gasoline vehicle, as the fuel cost of the engine warmup cycle is amortized over a short distance. Only all-electric vehicles escape this cold engine start penalty. (My very crude rule of thumb is that cold starts cost the same fuel as moving 2 miles on a warm engine, e.g. a 3 mile trip from a cold start takes the same fuel as 5 miles on a warm engine. Not a perfect rule, just a guideline.) The EPA city test cycles are much longer, 7.5 miles in an older version, 11 miles in a new version.

    If your commute is 3 miles round trip, not one way, that means two cold starts in that distance, making the mpg situation even worse.

    What tires does it have? The replacements now mounted may not have the same low rolling resistance as the factory tires. And what is their air pressure? Winter temperatures reduce the pressure, so they may need to be pumped back up.

    You can't reach the EPA rating at 70 mph unless conditions are perfect, and winter is not. MPG falls as speed increases. Here is a chart for the Liftback, your 'v' wagon model will get lower numbers, though a similar shape vs speed:
    Updated MPG vs MPH chart

    Note that PWR mode won't actually get you up to highway speed any faster, it just changes the pedal feel. It is mostly a human interface thing, use whatever mode feels or works best for you. The maximum available power is the same in all modes, when the pedal is pushed all the way down. (These modes do cause minor mpg differences in cruise control, cabin climate control, and engine auto-shutoff vs coolant temperature, but should be too small to be part of your issue.)

    ===============
    Here is another long-ago PriusChat writeup:
    Why Don't I Get The EPA Mileage?
     
    #6 fuzzy1, Dec 24, 2019
    Last edited: Dec 24, 2019
    dig4dirt likes this.
  7. Weirderal

    Weirderal New Member

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    Thank you for your replies, everyone!
    Point of clarification, I definitely don't reach 70 miles per hour in my commute, just that I use that speed when I'm on the highway for out-of-town affairs a few times a month.
    The fastest speed I reach in my commute is around 45. I pass about 12 stoplights on the way and usually end up stopped at 3-6 of them.

    It has been cold here, so I've been using the heat (I leave it on floor/defog) for my commute. Didn't realize that might be having such a huge impact. The EV light does come on a few times at the later lights before my workplace, so I'm assuming that means it's "warmed up", but I understand that still means it spent more fuel than would be necessary in the summer.

    All tires are 205/60R16. Front are Uniroyal Tiger Paw AWP3 and rear are Laufenn G Fit AS. I put them all at 33 psi (per sticker recommendation) when we had a cold snap a couple weeks ago and the tire pressure warning came on.

    I'll ask my mechanic about cleaning the EGR circuit next service and look into the oil catch can. I definitely don't like getting my hands dirty beyond "refilling fluids" and minor interior work. I've replaced all the bulbs with LEDs and that's about the extent of my willingness to work on it.

    I'm still thrilled to be getting this kind of fuel economy; I was just a little stunned because my previous vehicle, at least, had been VERY consistent in its fuel economy, so a fluctuation of 6 mpg was a surprise for me. Then again, that's basically the same percentage of fluctuation I got in my last vehicle. I'd been driving that van for 7 years (basically since I got my license) so I guess I really internalized the low numbers.
     
  8. fuzzy1

    fuzzy1 Senior Member

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    The math of the American MPG scale magnifies small differences on efficient cars, while masking larger differences on gas hogs. The math of the Euro/Canadian scale, liters-per-100km, doesn't do the same.

    On top of that, I wouldn't be the least bit surprised if gas hogs show a lower percentage variation than efficient cars. Several of the factors that vary will be a small portion of their total energy use.
     
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  9. aburnham2

    aburnham2 Junior Member

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    Twice I have improved milage on a Prius. The first was a 2007 now my brothers 2012 Prius V. Let the tank get down very low, add two 12 oz containers of Techron (Walmart $5 each). Drive 10 miles to a gas station and fill up. I got a 10 MPG improvement on the 2007 and a 4 MPG on the V. Highway on the V in winter seems to be 35-36 MPG at 65 MPH. 75 MPH drops it to 31. Good luck.
     
  10. mikefocke

    mikefocke Prius v Three 2012, Avalon 2011

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    One thing you can do is shut off the heater and defroster if that is safe. Engine warms up faster. Then turn it on once the enine is fully up to speed. That gets you to the hybrid capable point faster..

    Another is up those PSI in your tires. I was running up to 40 in the summer so maybe 36 to 38 in the winter. My current Rav4 was delivered by mistake with 50 PSI. I ran it at those pressures for 2k miles before I had a reason to check and reduce them to 36.
     
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